Introduction to Airfoil

By | February 10, 2015

What is Airfoil?

The special shape of airplane wing is called airfoil. It is designed in a way to create less pressure above the wing.

Introduction to Airfoil

   An airfoil (in American English) or an aerofoil (in British English) is the shape of a wing or blade in cross section.  An Airfoil shaped body moved through a fluid produces an aerodynamic force. The component of this force perpendicular to the direction of motion is called lift. The component parallel to direction of motion is called drag.

   The lift of an airfoil is primarily the result of angle of attack and shape (in particular its chamber). When either is positive, the resulting flow field about the airfoil has a higher average velocity on the upper surface than the lower surface. This velocity difference is necessarily accompanied by a pressure difference (via Bernoulli’s principle) which in turn produces lift force. The lift force can also be related to the average top/bottom velocity difference without invoking the pressure by using the concept of circulation. Airfoil design is a major facet of aerodynamics. A fixed-wing aircraft’s wings, horizontal and vertical built with airfoil-shaped cross sections. Swimming and flying creatures also employ airfoils. Any object with an angle of attack in air or moving fluid such as a flat plate will generate aerodynamic force called lift.

         Airfoils are more efficient lifting shapes able to generate more lift (up to a point) with less drag. this has to be the most primary and basic characteristics to be kept in mind while designing an airfoil for a wing span. Various airfoils serve different flight regimes. Asymmetric airfoils can generate lift at zero angle of attack while a symmetric airfoil may better suit frequent inverted flight as in aerobatic airplane. The cross section is not strictly circular however the radius of curvature is increased before the wing achieves maximum thickness to minimize the chance of boundary layer separation this elongates the wing and moves the point of maximum thickness back from the leading edge.

The cross sectional view of an airfoil in introduction to airfoil

Fig : cross sectional view of an airfoil


   Could it be imagined how an aircraft gets in to air? It goes this way i.e. when the earliest serious work on the development of the airfoil sections began in the late 1800’s. Although it was just known that flat plates would produce lift when set at an angle of incidence some suspected that the shapes with curvature that more closely resembled the bird wings would produce more lift or do so, more efficiently. Sir H.F.Phiips patented a series of airfoil designs when he tested them in his earliest wind tunnel experiments.

   The wide range of operating conditions and constraints generally makes the use of an existing “cat log” section not the best. These days airfoils are designed for their intended application. This document tries to optimise the design of airfoil with the help of airfoil simulator.

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